The Swine Flu and You

As of Sunday, May 3, 2009, the World Health Organization (WHO) had reported 898 cases of influenza A(H1N1) infection across 18 countries, and higher numbers will certainly follow in the coming days and weeks. With infection spanning from the United States to New Zealand, the virus has thus far been implicated in 20 deaths. However, in the United States alone, it has been postulated that, in a "worst case scenario," A(H1N1) infection will result up to 1,700 new cases by the end of the month. Influenza A(H1N1), more popularly known as the swine flu, has therefore taken the world and media outlets by storm in the past week, promoting sensationalist mass hysteria and fueling the fears of a worldwide pandemic. However, prior to swearing off ham sandwiches and canceling those travel plans, there are a few simple and a few scientific facts that it would benefit everyone to know about influenza.

Influenza is an infectious disease that is directly resultant of contamination by an RNA virus of the Orthomixoviridae family. Orthomyxoviridae viruses are capable of infecting both birds and mammals. The rapid mutation and reassortment of influenza strains in response to treatment hampers definitive vaccine development as well as other prophylactic tactics. Three types of the virus - A, B, and C - are capable of infecting humans, although infection via a type C virus is rare. Meanwhile, both A and B type viruses are capable of causing epidemics in human populations; however, only type A viruses are implicated in global pandemics.

The influenza type A virus, such as the one responsible for the swine flu, is capable of causing global pandemics due to a phenomenon known as antigenic shift. This profound antigenic variation occurs only in type A viruses. Two viral surface glycoproteins, known as hemagglutinin (HA) and neuraminidase (NA), are integral to infection. Variations in HA and NA surface expression provide a distinct viral profile upon which evolution may act. There are, for example, 16 HA and 9 NA subtypes known to birds, but only HA 1, 2, and 3, and NA 1 and 2 are commonly found in humans. The reassortment of gene segments between co-infecting viruses propagates the evolution of novel HA and NA antigen expression.

Pigs, for instance, are susceptible to and may become infected with both avian and human influenza type A viruses. If both avian and human viruses infect a cell within the pig, and both viruses successfully replicate, then the assembly of viral progeny within the cell presents the virus with the opportunity to reassort the genome segments of HA and NA. This results in the production of an entirely new viral strain, for which the human population has no acquired immunity and is dangerously susceptible.

However, on the eve of a proposed worldwide A(H1N1) pandemic, it is imperative not only to understand how this virus has evolved, but also the mechanism behind its transmission, as well as common symptoms and tips for disease prevention:

1. Transmission: Don't blame the swine! Outbreaks in humans are currently occurring via human-to-human transmission - and, in some cases, the humans are even the ones infecting the pigs! Influenza is a respiratory illness, and infection may therefore occur via inhalation of contaminated air droplets, as well as by close contact with infected surfaces (such as unwashed hands). Although anyone who has not previously been infected is at risk of contracting the virus, particularly high-risk groups such as the elderly, infants, and expectant mothers should take the necessary precautions to promote proper sanitation and good hygiene.

2. Symptoms: The signs and symptoms of A(H1N1) are in fact very similar to those of a regular influenza infection - including fever, cough, headache, myalgia and arthralgia, sore throat, runny nose, and occasionally nausea, vomiting, or diarrhea. However, mortality can vary widely between different countries, as has been observed between Mexico and the United States. Although the mortality of many infectious diseases is concentrated in the developing world, genetic differences in the viruses as well as the presence of co-infecting pathogens (for example, bacterial pneumonia) may have contributed to the increased number of Mexican A(H1N1) fatalities.

3. Prevention: To prevent transmission, the WHO recommends using good personal health and hygiene habits, such as regular hand-washing, as well as covering the nose and mouth with a tissue when sneezing or coughing. Hand-washing with soap and water, or by the use of alcohol-based hand sanitizers such as Germ-X or Purell, is particularly effective at preventing the spread of infection and reducing the threat of a pandemic.

Recent indications of A(H1N1) strain weakening are optimistic, although the final outcome of the virus remains to be seen. Misinformation is still running rampant in the media, and the future development of a swine flu vaccine by the WHO is currently undecided. However, unless that plane you're on is flying to Mexico, it's safe to say that your ham sandwich and your vacation are both safe to enjoy.

World Health Organization

Centers for Disease Control and Prevention

CNN - Canada: Farmer possibly gave swine flu to pigs

Robin Lloyd, LiveScience - 'Worst Case' Scenario for Flu Estimated

Maria Cheng, Associated Press - WHO will take vaccine gamble with swine flue